Yes, it's the airline's internal way of distinguishing cards for different configurations that affect safety and evacuations. Some airlines will additionally use colour-coding or other such things.
Sometimes though airlines can use existing identifiers - Qantas for example marked their 767 safety cards "767-336" and "767-338" as the ex-BA -336s had different door layouts, while other types were simply "747-400" or "737-800" and so on as they had consistent configurations.
(my memory is also telling me the 767-336 safety cards had the registrations of the aircraft to which they were applicable shown on the back, but that could be me confusing them with the seat maps)